The iMac Pro features new apple custom silicon: the T2 chip. It integrates previously discrete components, like the SMC, ISP for the camera, audio control, SSD control... plus a secure enclave, and a hardware encryption engine. This new chip means storage encryption keys pass from the secure enclave to the hardware encryption engine in-chip - your key never leaves the chip. And, they it allows for hardware verification of OS, kernel, boot loader, firmware, etc. (This can be disabled...)

The screenshot he posted shows what the hardware verification dialog for things like the operating system and bootloader looks like. As long as we can turn security measures like this off - as we can on, e.g., Chromebooks - this is a good development. Now all we have to do is hope these companies don't abuse this kind of technology.